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Method of purifying silicon utilizing cascading process

  • US 8,580,218 B2
  • Filed: 06/12/2012
  • Issued: 11/12/2013
  • Est. Priority Date: 08/21/2009
  • Status: Active Grant
First Claim
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1. A method for purifying metallurgical grade (MG) silicon, comprising:

  • (a) contacting a first silicon with a second mother liquor, to provide a first mixture;

    (b) melting the first mixture to a temperature above the liquidus, to provide a first molten mixture;

    (c) cooling the first molten mixture to a temperature below the solidus, to form first silicon crystals and a third mother liquor;

    (d) separating the first silicon crystals and the third mother liquor;

    (e) contacting the first silicon crystals and a first mother liquor, to provide a second mixture;

    (f) melting the second mixture to a temperature above the liquidus, to provide a second molten mixture;

    (g) cooling the second molten mixture to a temperature below the solidus, to form second silicon crystals and a second mother liquor;

    (h) separating the second silicon crystals and the second mother liquor;

    (i) contacting the second silicon crystals with a first solvent metal, to provide a third mixture;

    (j) melting the third mixture to a temperature above the liquidus, to provide a third molten mixture;

    (k) cooling the third molten mixture to a temperature below the solidus, to form third silicon crystals and a first mother liquor; and

    (l) separating the third silicon crystals and the first mother liquor;

    wherein the mother liquors and the first solvent metal comprise a solvent metal;

    wherein the method provides upgraded metallurgical-grade (UMG) silicon; and

    further comprising combining the first mother liquor with at least a portion of the second mother liquor prior to contacting the first mother liquor with the first silicon crystals.

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